Editing Lexington-class aircraft carrier (section)

===Propulsion===
[[Turbo-electric transmission|Turbo-electric propulsion]] had been chosen for the battlecruisers because American companies struggled to produce the very large geared [[turbine]]s necessary for such big ships and was retained when they were converted into aircraft carriers.<ref name="ab311"/> One advantage of turbo-electric drive was that the substitution of flexible electric cables for bulky steam-lines allowed the motors to be mounted farther aft; this reduced vibration and weight by shortening the [[propeller shaft (ship)|propeller shaft]]s. Another was the ability to go astern at full power without needing a separate reverse turbine to do so, simply by reversing the [[electrical polarity]] of the motors. Other benefits were the ability to operate all four propellers if one of the [[turbo generator]]s failed, and the possibility of operating only some of the generators at low speed with suitably higher loading and greater efficiency.<ref name=breyer218>Breyer, p. 218</ref> "[Turbo-electric drive] was efficient, rugged and always reliable. But it was also heavy, intricate, and not easy to maintain and keep tuned up."<ref name=ab12>Anderson and Baker, p. 312</ref> The machinery also required special ventilation measures to dissipate heat and to keep out any salt air.<ref>W. McClelland, quoted in Anderson and Baker, p. 327</ref> Even with this and elaborate insulation measures, protection from moisture or from flooding due to battle damage or other causes remained problematic and it posed the danger of high voltage to the crew if damaged.<ref name=breyer218/>

Each propeller was {{convert|14|ft|9|in|m}} in diameter and each of the four propeller shafts was powered by two {{convert|22500|shp|lk=in|adj=on}} [[electric motor]]s acting in tandem. These motors were about five times the size of any earlier electric motor.<ref name=ab12/> Four [[General Electric]] turbo generators powered each propeller shaft and each was rated at {{convert|35200|kW}}, 5000 [[volt]]s and 4620 [[ampere|amp]]s of [[direct current]] (DC). Each of the four [[alternating current|AC]] [[alternator]]s produced 40,000 [[Volt-ampere|kVA]]. Sixteen [[water-tube boiler]]s, each in their own individual compartment, provided steam for the generators at a working pressure of {{convert|295|psi|kPa kg/cm2|0|abbr=on|lk=on}} and a temperature of {{convert|460|°F}}. The turbo-electric machinery of the ''Lexington''-class ships was designed to produce a total of {{convert|180000|shp}} and propel the ships at {{convert|33.25|kn}}, but each ship reached over {{convert|202000|shp|abbr=on}} and {{convert|34.5|knots}} in [[sea trial]]s in 1928. Six {{convert|750|kW|adj=on}} DC turbo generators were installed in the upper levels of the two main turbine compartments.<ref name=ab12/>

The ships carried a maximum of {{convert|6688|LT|t}} of [[fuel oil]], but only {{convert|5400|LT|t}} of that was usable as the rest had to be retained as [[Sailing ballast|ballast]] in the port fuel tanks to offset the weight of the island and main guns. They demonstrated a range of {{convert|9910|nmi|lk=in}} at a speed of {{convert|10.7|kn}} with {{convert|4540|LT|t}} of oil.<ref name=ab13>Anderson and Baker, p. 313</ref>